The Chuos Formation in the study area comprises mainly diamictite with minor interbedded feldspar quartzites and magnetite quartzites. The diamictites and bedded units are thought to have been deposited in a subaqueous environment by mass-flow processes, including mudflows, turbidity currents and grain flows. The widespread occurrence of extra-basinal clasts in the diamictite and the presence of dropstones indicate a glacial influence on Chuos deposition. Syn-sedimentary faulting appears to have caused much of the thickness variations within the Chuos Formation. The depositional setting in the study area appears to have been a halfgraben, with a fault-bounded, steepsided south-eastern margin, and a gently sloping north-western side. A model invoking redeposition of glacially-derived material down the slope of a tectonically active basin margin could account for most of the features observed in the Chuos Formation in the area.